The method relies on the use of aircraft stability derivative methods with the basic geometric and aerodynamic properties of the airship.
NASA’s Jet Propulsion Laboratory, Pasadena, California
Saturn’s moon Titan is of high interest for in situ study due to its many intriguing features. This moon has a dense atmosphere; rough, icy terrain; and low surface winds that make it the ideal place to send a controlled aerial robotic platform, such as a conceptual Aerobot Airship. An important feature of a self-propelled, lighter-than-air aerial vehicle is that it must be autonomously controlled to navigate and avoid obstacles because of a 2.6-hour communication delay between the Earth and Titan. Developing a dynamic model that can be tuned will enable robust and reliable control of the Aerobot Airship.

The solutions guarantee minimum fuel usage, satisfaction of position constraints, and adherence to thrust magnitudes that are within physical minimum and maximum limits.
NASA’s Jet Propulsion Laboratory, Pasadena, California
The Powered Descent Guidance (PDG) software provides a computationally efficient guidance algorithm for powered descent that ensures satisfaction of the governing dynamics, along with adherence to physical control and state constraints, such as avoid the surface, limit thrust magnitude and pointing, and divert based on available fuel. The software can generate guidance profiles for precision landing (or pinpoint landing when feasible) and also incorporate smart diverts to avoid the backshell landing corridor.

The effect of free-play in a system can be accurately estimated without the need for simulation.
Neil A. Armstrong Flight Research Center, Edwards, California
Aerodynamic control surfaces, with excessive free-play, can cause limit cycle oscillations (LCO), a sustained vibration of constant amplitude. The LCO is caused by a combination of aeroservoelastic effects and free-play. If the amplitude is sufficiently large, it can impact handling qualities, ride quality, and can cause structural fatigue, ultimately leading to structural failure. Free-play is typically distributed throughout the actuator and control surface, with contributions from actuator mounting bearings as well as the surface hinge.

John H. Glenn Research Center, Cleveland, Ohio
Many of the most challenging aspects of propulsion system development are related to the prediction of interacting effects among fluid loads, thermal loads, and structural deflection. A typical design practice might ignore the interaction between the physical phenomena where the outcome of each analysis can be heavily dependent on the inputs. Such a rigid design process also lacks the flexibility to employ multiple levels of fidelity in the analysis of each of the components.

Lyndon B. Johnson Space Center, Houston, Texas
An easy-to-use design tool was developed in response to a large number of documented cases of critical (flight and ground) hardware failing after experiencing drops during commercial shipment. By entering the mass of the hardware to be protected, and the drop height, the software helps the user select the type and dimensions of the shock attenuating foam needed. Hundreds of drop tests were conducted with metal plates instrumented with accelerometers that were protected by common shipping foams of different thicknesses, along with foam compression tests conducted at various speeds to develop mathematical material models for these foams. The foam drops were video recorded at a very high rate of speed to capture foam deformation due to drop.

Goddard Space Flight Center, Greenbelt, Maryland
The Evolutionary Mission Trajectory Generator (EMTG) is a global trajectory optimization tool for designing interplanetary missions that perform multiple flybys and either low-thrust or high-thrust propulsive maneuvers on the way to destinations in the solar system. Some targets, such as Mars and Venus, are reachable using direct flights with chemical propulsion technology. Others, such as Mercury, main-belt asteroids, and comets are not easily accessible. One way to mitigate this problem is by using more efficient propulsion systems, such as low-thrust solar electric propulsion. Another is to find more efficient paths to the destination, possibly including gravity assist maneuvers, or planetary flybys.

Question of the Week

This week's Question: This month, the Federal Aviation Administration proposed long-awaited rules on the commercial use of small drones, requiring operators to be certified, fly only during daylight, and keep their aircraft in sight. The ruling,...